Transmitter array antennas, sometimes designated by the term “transmit-array antenna”, are commonly used in the 1-100 GHz frequency domain for focusing a radiation; for this reason, they are therefore often also called discrete-lens antennas.
Array antennas of such a type comprise a large number of individual radiating cells able to receive an electromagnetic field on one face and to transmit it on the opposite face with minimum attenuation and a known phase shift. Antennas of this type are generally known for forming a wave projector, transforming at their output the properties of the wave entering at their input.
As illustrated in FIG. 1, an example of an array antenna is given which comprises a reception surface 111 which is generally illuminated by one or more primary sources 101, the other surface 112, also called the transmission surface, constituting the radiating aperture of the antenna.
The two surfaces 111 and 112 are generally separated by a phase shift device 113 so as to allow the modification of the phase and of the direction of the radiation emitted by the primary source or sources.
The antennal array operates in an identical manner in transmission or reception as long as the array does not contain any non-reciprocal element such as an amplifier or certain magnetic components. In the converse case, the antennal array is designed to operate exclusively either in transmission, or in reception.
The widely prevalent transmitter arrays used in military applications and/or general-public communication systems, comprise multiple advantages, notably:                energy efficiency at high microwave frequencies (of the order of several GHz and beyond) by virtue of the transmission by radiation in the air between the primary source and the phase shift cells;        simplicity and cost of implementation for arrays comprising a large number of elements (several hundred and beyond) corresponding to very directional antennas;        reduced bulk, mass, and cost of implementation by virtue of the fact that these arrays are implemented in planar technology, generally on printed circuit;        a radiation pattern provided with good polarization purity by virtue of the array structure based on elementary antennas whose imperfections can mutually compensate one another and make it possible to generate a beam with very pure linear or circular polarization;        good quality of the radiation pattern at the level of the shape of the beam and of the sidelobes by virtue of the position of the primary source situated in the opposite direction to the direction of the principal beam generated by the array.        
To extend the possibilities offered by these transmitter arrays, efficient and uncomplicated systems have been designed in compact form, though their output beam (or the phase/direction of radiation) is fixed. However, research has been conducted to make it possible to have systems for which it is possible to control the phase shift in transmission in an electronic manner in order to control the radiation pattern of the antenna and thus off-set the beam and/or modify its shape. Several techniques have been proposed for these purposes.
For example, a reconfigurable (nonsymmetric) cell using radiating slots as antennas, perpendicular to one another and situated on either side of an assemblage of two substrates, has been proposed in the international patent application referenced under the publication number WO2009023551.
Resonators in segments arranged between the two slots make it possible to ensure electromagnetic coupling between these two slots, and breakers placed at various points of these resonators make it possible to select a mode of coupling from four possible modes, each mode corresponding to transmission phases differing from one another by 90°.
The resonators of this structure form a filter, each segment of these resonators forms a resonating circuit coupled to a slot antenna. By actuating the breakers, the resonant frequency of the complete structure is modified.
This cell therefore makes it possible to generate four phase states with low transmission losses.
However, a drawback of this cell is its narrow passband (of the order of a few percent), which is a direct consequence of the use of the coupling technique, which relies on resonators necessarily having a frequency dispersion of significant phase.
Another technique, in the form of a transmitter array completely separating the two antennas and the phase shift circuit has been proposed in A. Munoz-Acevedo, P. Padilla, M. Sierra-Castaner, “Ku band Active transmitarray based on microwave phase shifters,” European Conference on Antennas and Propagation, 2009. This approach makes it possible to use a phase shift circuit covering the whole of the possible 360° phase range.
However, the implementation of such a transmitter array is complicated since it requires non-integrated phase shifters, which are therefore of large dimensions, connected perpendicularly to the plane of the antennas.
Also, a reconfigurable cell comprising two patch antennas separated by a ground plane and coupled by a slot, termed the coupling slot, made in the ground plane, is known from J. Y. Lau, S. V. Hum, “A low-cost reconfigurable transmitarray element,” IEEE AP-S Int. Symp., 2009. Each patch antenna is separated into two parts by a median slot. Variable-capacitance diodes are placed on these slots as well as on the coupling slot. By controlling the bias voltage of these diodes, the resonant frequency of the patches and of the coupling slot varies as does the transmission phase over a range of as much as 360°.
The principal advantage of this solution is to allow a continuous variation of the transmission phase over a significant range of close to 360°.
However, the experimental results have revealed several drawbacks:                a significant level of loss of the order of 3 dB and varying in an appreciable manner as a function of the transmission phase;        a narrow passband due to the use of resonators;        a high number of components and complicated means of control of the components, the control lines having to be connected to the radiating elements, so giving rise, moreover, to appreciable perturbations.        